The present invention relates generally to a method for manufacturing a semiconductor package, and more particularly to a method for manufacturing a semiconductor package having an improved bump structure.
Recent semiconductor design trends relate to semiconductor chips capable of storing and processing vast amounts of data quickly and semiconductor packages having the semiconductor chips mounted to circuit boards.
Chip scale packages having a size no greater than 100% to 105% of the size of a semiconductor chip have been disclosed in the art.
A flip chip package is one type of chip scale package. The flip chip package includes bump structures formed on a substrate, which are connected to the bonding pads of a semiconductor chip. The flip chip package can significantly reduce the size of the semiconductor package.
However, as the size of semiconductor chips continues to decrease, the size of bonding pads and/or the gap between adjacent bonding pads decreases as well. Such decreases in the size of bump structures on the substrate and the gap between the bump structures lead to difficulties in forming the bump structures.
Bump structures having the shape of protrusions may be formed by etching a metal layer through a wet etching process.
However, forming the bump structures having the shape of protrusions by etching a metal layer has several disadvantages. First, forming the bump structures having the shape of protrusions by etching a metal layer is a slow and time consuming process. Second, forming the bump structures having the shape of protrusions by etching a metal layer results in the bump structures having non-uniform sizes. When the bump structures have non-uniform sizes, the electrical connections between the semiconductor chip and the bump structures are of poor quality.
Also, when the bump structures having the shape of protrusions are formed by isotropically etching a metal layer, the area of the upper portions of the bump structures is likely to become smaller than the area of the lower portions of the bump structures, and therefore the connection area between the bump structures and the bonding pads is decreased.
Further, when forming the bump structures having the shape of protrusions by etching a metal layer, as the height of the bump structures increases, the thickness of the metal layer increases. As the height and thickness of the bump structures increases, forming the bump structures becomes increasingly more difficult and defects are likely to occur in the bump structures.